Python: most idiomatic way to convert None to empty string?

Question

What is the most idiomatic way to do the following?

def xstr(s):
    if s is None:
        return \'\'
    else:
        return s

s = xstr(a) + xstr(b)


        

Answer 1

If it is about formatting strings, you can do the following:

from string import Formatter

class NoneAsEmptyFormatter(Formatter):
    def get_value(self, key, args, kwargs):
        v = super().get_value(key, args, kwargs)
        return '' if v is None else v

fmt = NoneAsEmptyFormatter()
s = fmt.format('{}{}', a, b)

Answer 2

def xstr(s):
    return s if s else ''

s = "%s%s" % (xstr(a), xstr(b))

Answer 3

def xstr(s):
   return s or ""

Answer 4

Functional way (one-liner)

xstr = lambda s: '' if s is None else s